No. I.] THE EGG OF UMAX AGRESTIS. 215 



Fig. 39. What the function of these bodies is I have not been 

 able to determine. 



During the stage of the second maturation spindle I have 

 been fortunate enough to find an apparently normal egg in 

 which the sperm is accompanied by two tiny asters. The 

 sperm-head, the sperm-asters, and a part of the second matu- 

 ration spindle are shown in PL XI, Fig. 20, a, b, b', and c. 

 The asters lie some distance away from the sperm, and between 

 the sperm-head and the maturation spindle. These relations of 

 the sperm-head, the asters, and the maturation spindle are pre- 

 cisely similar to those figured by Kostanecki and Wierzejski 

 for Physa,^ and also to those described by Wilson, Boveri, and 

 Hill for the echinoderm, and by Wilson and by Mead for the 

 annelid. During the formation of the second polar spindle the 

 sperm-head becomes more and more vesicular and moves away 

 from the periphery of the tgg, in toward the egg-astrosphaere. 

 I have found a single tgg in which the centrosome and aster 

 are present, in connection with the sperm-nucleus, immediately 

 after the extrusion of the second polar globule, but the Qgg 

 is evidently abnormal. Sections through the sperm-nucleus of 

 this Qgg are shown in PI. XII, Fig. 21, a, b, and b\ The 

 nucleus is enormously distended and completely enclosed by 

 the rays of a spiral aster, which is formed about a deeply 

 staining granule — the centrosome. There is so little chro- 

 matin in the nucleus that it is barely perceptible in the 

 sections. I have repeatedly studied the early maturation 

 stages of Limax agrestis in the hope of finding other asters; 

 but, except in the two cases just described, I have found only 

 two or three extremely doubtful cases. These cases, however, 

 are of especial interest, for they serve to throw light on a 

 problem that in Limax agrestis is extremely difficult of solu- 

 tion. They show that in all probability, even in these very 

 early stages, structures are present in the cell which do not 

 usually manifest themselves until a much later period, although 

 in most of the forms that have been carefully studied — echino- 

 derms, mollusks, and worms — the sperm-asters appear very 

 soon after the spermatozoon has entered the &gg. When the 



'^ Archiv f. mikr. Anat., Bd. xlvii, 1896, PI. XVIII, Fig. 11. 



